Mechanical stresses in oxide thin films

Based on Hartmann-Shack sensor technique, an online thin film stress measuring system was introduced to measure the film stresses of TiO 2 and SiO 2 , and comparison was made between the film stresses prepared respectively by the conventional process and the ion-beam assisted deposition. The effect of ion-beam assisted deposition on the film stresses of TiO 2 and SiO 2 was investigated in details, and the stress control methodologies using on-line adjustment and film doping were put forward. The results show that the film stress value of TiO 2 prepared by ion-beam assisted deposition is 40 MPa lower than that prepared by conventional process, and the stress of TiO 2 film changes gradually from tensile stress into compressive stress with increasing ion energy; while the film stress of SiO 2 is a tensile stress under ion-beam assisted deposition because of the ion-beam sputtering effect, and the film refractive index decreases with increasing ion energy. A dynamic film stress control can be achieved through in-situ adjustment of the processing parameters based on the online film stress measuring technique, and the intrinsic stress of film can be effectively changed through film doping.

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Current-Dependent Resistance in TES Wiring Superimposed Nb Striplines

Ferrari Barusso,

Celasco,

Gallucci

et al. 2024

J Low Temp Phys

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During the characterization of the demonstration model of the Cryogenic AntiCoincidence (CryoAC) Detector (ACS-10), a current-dependent parasitic resistance was found in series with the TES network on board the detector. Analysis was possible because the resistance rises for currents above 11 $$\mu$$ μ A, and is therefore not observed at low bias excitation. A comparison of measurements of the TES across its Nb wiring at different temperatures suggested that the source of resistance was in the wiring and not in the TES network. After several analysis of the wiring fabrication steps, FIB-FE-SEM studies of film sections and tests of niobium film quality, we understood that the parasitic resistance was due to point contact in the Nb step coverage caused by film cracks. The fracture was due to the wall steepness and thickness of the films, since rapid step coverage is less mechanically stable and the stress on the films is proportional to the fourth power of the thickness. Therefore, all thicknesses in the wiring were reduced to the minimum optimum step coverage values and the first negative lithography parameters were optimized to reduce the wall film angle. The samples after this optimization showed no current-dependent series resistance to TES.

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Mechanical stresses in oxide thin films

Cited by 5 publications

References 9 publications

Properties and Characterization of Dielectric Thin Films

Properties and Characterization of Dielectric Thin Films

Effect of ion-beam assisted deposition on the film stresses of TiO2 and SiO2 and stress control

Current-Dependent Resistance in TES Wiring Superimposed Nb Striplines

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